To maintain a robust strategic deterrence, the United States
splits its nuclear delivery systems across three viable paths – nuclear-capable bombers,
submarine-launched ballistic missiles, and land-based missile silos. These
three deterrents make up the US nuclear triad, a concept we will explain soon!
The United States began to build nuclear missile silos in 1959, when the technology
for intercontinental ballistic missiles (ICBMs) began to become available. These silos,
which now house the Minuteman III ICBM complete with their 400 kiloton nuclear warheads, stretched
from Montana to Missouri at their peak. After the end of the Cold War, many of these missile silos
were decommissioned, but as of 2020, 400 Minuteman silos remain active in the Great Plains. There are
also many more decommissioned sites from the earlier Peacekeeper, Titan, and Atlas ICBM
programs, some of which are even available for private purchase if you can pony up the cash.
Why did the Air Force, the branch of the armed forces that controls the ICBM program,
decide to build the current Minuteman silos only in the Great Plains states?
There were several good reasons for the site selection. Well, the Great Plains
had the shortest launch trajectory to attack targets in the Soviet Union,
as missiles there would have an easier time going over the North Pole and reaching their designated
targets in the USSR’s territory. The Great Plains are also far enough away from the coasts to
give America enough time to launch a counter offensive in case it came under attack from
submarine-launched ballistic missiles. The places around these silos are also sparsely-populated,
meaning that enemy attacks on the ICBM silos would leave comparatively-minimal collateral
damage. Finally, being so deep into the interior of the United States naturally
meant that these silos were and still are well beyond the reach of a conventional enemy attack.
Their location was not the only means of defense that the silos had. Minuteman and other ballistic
missile silos were constructed as underground fortresses, parts of which stretch hundreds
of feet deep. In fact, a couple of years ago, a rich businessman in Kansas bought
a decommissioned silo that stretched 150 feet underground. He went on to turn it into a luxury
survival condo. Being buried deep underground makes these silos harder to attack. Their depth
serves as a formidable layer of security that many value in case of a nuclear war.
Getting into a nuclear missile silo, one that’s active, anyway, is far from easy. Ironically,
nuclear silos are located on private lands, where the landowner has an incentive to
prevent trespassing or other shenanigans. The silos’ first line of defense is a fence.
Beyond it is a radar security sensor that will detect any object on the ground beyond
the fence. If someone or something fishy is making waves, word will be sent to the
numerous fully-armed two-man Security Response teams who will investigate the disturbance.
If you check out as an approved visitor, you will need a security code to go through
the Personnel Access Hatch, which weighs over 2,000 pounds, so you’re better-off not trying
to break through it. Afterward, you must travel through a 90-foot shaft that ends with a 14,000
pound barrier device known as the “B-Plug.” Don’t try to break through this one, either,
as nothing you have will work, even if you brought a jackhammer or powerful explosives.
Only a second security code will allow one to pass this point. Out of concern that these plugs
would not allow fast-enough access to thwart an internal attack in the unlikely event that
a group of terrorists were to infiltrate the silo while the B-Plug permits access, newer,
faster-operating ones were installed in the late 2000s, and now these are being further
upgraded. Thanks to these new devices, which have their own unique energy sources by use
of a fast-spinning flywheel, nuclear silos are better-protected against unconventional attacks.
A silo’s construction materials are another form of defense. They are built to withstand
earthquakes and other natural or manmade disasters. Shock absorbers are built around
sensitive electronic equipment. In their main makeup, nuclear missile silos are constructed from
heavily reinforced concrete. The aforementioned silo in Kansas has concrete walls that are nine
feet thick. Some of the reinforced concrete in Minuteman silos is designed to withstand
pressures of up to 2,000 PSI. Although this sounds impressive, it’s not enough to withstand a nearby
nuclear blast, even if it is not a direct hit, and modern ICBM warheads are so accurate that
they would almost certainly experience a direct hit if these silos were to become a target. This
vulnerability is one of the reasons why some defense observers argue that the land-based ICBM
program should be scrapped altogether, as unlike submarines and bombers, silos are stationary,
and sitting ducks in the event that the worst comes to happen. On the other hand,
the silos are designed to be able to survive a nuclear attack by being spaced far enough
away from one another as to make a complete decapitation of their capability unlikely. The
surviving silos would then be able to launch a retaliatory nuclear strike. For example,
the South Dakota Minuteman missile field at its peak in 1987, stretched across much of the western
part of the state. It would take a sophisticated strike indeed to knock all of them out before at
least some of them would be able to retaliate. The South Dakota field has since been decommissioned,
but many such missile fields remain in service in states like North Dakota. The Air Force maintains
such capabilities to enhance the mission of deterrence, which is as much psychological as
physical. If an adversary knows that its first strike is likely to fail in removing America’s
ability to retaliate with its own nuclear weapons, an attempt at such a first strike becomes less
probable. This is an especially important fact to keep in mind as China builds 250 new ICBM-capable
missile silos in three separate fields as part of their modernization of its nuclear forces
in both quantity and quality, as fears of a new Cold War and nuclear arms race grow once again.
The process for launching an ICBM is surprisingly simple, though naturally, there are safeguards in
place to ensure that there are no mistaken or corrupted launches. First, the President
must decide that a nuclear launch is warranted. This decision may not be as simple as it seems,
since in any such apocalyptic scenario, he may have as little as seven minutes to be briefed and
make a decision, before enemy nuclear missiles may or may not impact the United States. There
have been several close calls where things appearing on radar have seemed like incoming
nuclear missiles but were not. For example, on March 15th, 1980, a Soviet submarine operating
near the Kuril Islands launched four missiles as part of a training exercise. An American
early warning radar system suggested that one of the missiles was heading for the United States,
which forced a conclave of defense officials to hastily convene and assess if the threat was real.
They concluded it was not, but this incident and others on both sides of the Iron Curtain, showed
how pressed for time leaders might be before being forced to make such a world-changing decision.
With hypersonic missiles on the way, we can expect the situation to get even worse in the future.
Should the President decide to authorize the launch, he will inform the National Military
Command Center (NMCC) at the Pentagon, which has a number of pre-packaged nuclear response scenarios
on standby. His identity must be verified first through use of a unique code. If that
code is valid, orders are sent to the launch crews, and all 400 of the Minuteman missiles
currently in service could be in the air within minutes of receiving the Presidential order.
This scenario is called the “launch-on-warning” scenario, which leaves little room for error. The
President also has the authority to authorize a nuclear first strike, largely under the same
procedures. In either scenario, once the President makes his decision, it is final.
As for the crew itself, there is a maze of failsafes that they must navigate in order
to successfully launch their payload. In the earlier Titan II program, a series of
electronic and mechanical waypoints needed to be passed in order to command the missile to launch.
For example, there was a lock that required inputting a six-digit code. There were only
seven chances to get the 17 million possible combinations correct. On the eighth attempt,
the lock would commit “electronic suicide.” And there was no way to hack the codes, either. If
you were trying to guess it, you’d need to do it “the old-fashioned way,” to use the words of
a director of the Titan II silo museum. The final step was for the crew commanders to turn separate
keys simultaneously for five seconds. These keys needed to be held in their proper position,
and it was impossible for one operator to turn both keys at the same time. Although the Titan
II program is retired, similar safeguards are in place for the current Minuteman program.
America’s nuclear missile silos, even those operating in the year 2022, have what seems
to be extremely primitive computing technology. You might be mistaken in thinking that it’s still
the 1970s or the 1980s if you actually get to step inside an active silo. The Minuteman’s
operating system is called the Strategic Automated Command and Control System (SACCS). Missileers,
as the personnel stationed in the silos are known, cannot simply Google their instructions
or retrieve them through a database. They must instead do research the old-fashioned way,
by flipping through mounds of paper in giant black folders to find the right instructions.
When computers are used, there are peculiarities you will find nowhere else. For many years,
the SACCS system still retained not only floppy discs, but the ancient eight-inch floppies. These
have finally been retired, but the smaller ones that you might remember if you had the
good fortune of experiencing the 80s and 90s remain in service. As the Air Force is currently
modernizing the ICBM program, these discs, too, are expected to go to the electronic graveyard,
but the Air Force had a good reason for the retention of the ancient systems. The SACCS
system is, ironically, far safer from cyber attacks than more modern software. The system
is not connected to the internet, and since it has no IP address, it cannot be hacked. Unfortunately,
this otherwise extremely attractive quality also means that maintenance on the system is harder,
since modern military engineers are inadequate, and the Air Force usually needs to call in
civilian specialists who can, among other things, solder metal. Newer systems will be
easier to maintain. Still, the silos won’t change overnight, as the Air Force will undoubtedly want
to ensure that robust safeguards are in place before replacing SACCS, as the realm of cyber
war grows more sophisticated. This means that this system will stay around for at least a few more
years. So for now, we can all sleep safely knowing that Russia, China, or Skynet won’t be able to
hack America’s ICBMs. There was one eerie incident that could have triggered such a scenario, though.
On October 23rd, 2010, Warren Air Force Base, Wyoming, lost control of its 50 live Minuteman
III missiles for nearly an hour. Had an unauthorized launch attempt come during
that window, there would have been no way for the Air Force to stop it. The cause of the incident
was later shown to be a faulty circuit card installed during routine maintenance of the
SACCS system. The incident is a reminder that despite the dangers of cyber warfare,
there are still good reasons to modernize the ICBM program.